Magnesium base alloys



@group of rare earth metals.

Patented Apr. 24,1951

UNITED STATES" PATIFLN'I'} ,OFFlC-El l Y 2,549,955 f Q l MAGNESIUM BASE ALLOYS I Alfred ClaudefJes'sup, Edward Fredericli-Emley,

and Philip Andrew Fisher, CliftonJunction,

near Manchester, England, assignorsto Magnesium Elektron Limited, Clifton Junction, near.

, Manchester, Englandga British company N6 Drawing. Application January 4, 1949, Serial No. 69,243. 'In Great Britain January 6, 10 18 2 Claims. (ems-1 s) This invention relates to magnesium its Object is to improve the mechanicalflpropeh ties of such alloys.

It has heretofore beenproposed to incorpo- ;v

.rate proportions of ceriumor misch metal in magnesium base alloys in order to improve mechanical properties, and in particular the resistance to creep at elevated temperatures, e. 'g. of the order of 200 C. v

It has furthermore been proposed in the specification of British Patent No. 540,333 to provide magnesium base alloys which incorporate misch metal from which the cerium has been substantially removed with a view to im proving the resistance of the alloys to corrosion I without losing their desirable. mechanical properties. This omission of cerium does not however appreciably affect the mechanical properties either harmfully or. desirably.- The op-'-- timum quantity of misch metal free from cerium to be introduced into the alloys was moreover specified to lie between and 10% of the .total alloy, which also contained appreciable Qpresent, if at all, in quantities not exceeding separately or together, the, balance, if any, being praseodymium and small quantities of samarium and traces of elements of the yttrium The praseodymium is therefore about 10 to 25% of the total of rare earth metals.

We have found that such alloys offer improved static mechanical properties, particularly in the cast state, as compared with alloys containing similar or greater proportions of misch metal (with and without cerium), or lanthanum. Moreover, the alloys of the present invention have an improved creep resistance at high temperatures as compared with alloys containing similar or higher proportions of cerium or misch metal (with and Without cerium) or 1anthanum.;

base al-- loys containing at least 85% of magnesium and of the following elements in the proportions stated:

Percent Zinc 0.5 to 10 Cadmium 0.5 to 10 Beryllium 0.0005 to 0.1. Mercury 0.01 to 5 Thorium 0.01 to 10 Calcium 0.01 to 0.2

The alloys of the present inventionalsol im ai' contain any otherjelementsknown in the mag,-

nesium base alloy art as alloying ingredients fin these alloys. If the alloys do not contain-zirconium, they may contain one or more of the following elements in the proportions stated:

.7 I Percent Manganese 0.02 to 2 Aluminium 0.01 to' 2,.- Calcium ..0,01 to 0.2 Thorium 0.01 to 10 Mercury 0.01 to 10.. Beryllium 0.0005 to -0.1 a V 0.5 to 10 Cadmium -0.5 A to 10 Wehave, moreover, ascertained that-a further Patent No. 511,137, and in particular increases Such alloys the elongate of sand cast objects. incorporating zirconium must be substantially free from elements which precipitate zirconium from a magnesium melt, e. g. aluminium,manganese, tin, silicon, cobalt, nickel and antimony. These alloys may, however, contain one or more In general when the alloys according to the present invention contain zirconium, they should of hydrochloric acid consisting of- 30 cos. of HCl (specific gravity 1.16) to'85 cos. of water, sufiicient acid being added during dissolution to maintain the initial concentration.

The alloys of the present invention offer advantages both in the cast and wroughtconditions.

0.7% Zr, 35% Zn,2%% misch-metal, 5.0 10 inch per 1' length Balance magnesium.-

What we-claimis:- 1. A' magnesium base alloy, consisting essentially of at-least 85-% magnesium and at least 0.41%: of zirconium; and from: :5 to 4% ofirare earth metals of which neodymium" constitutes at least.- 50% and in; which lanthanum; and: cerium do-not exceed25;%' together, the balanceof the rare.- earth metals being. praseodymiunr and small.quantities -ofisamarium and; traces of ele- Static Mechanical Properties are. as-

55 3 Stress,. Perscent tonlsqgin; 0112" 0.7% Zr, 2%? Zn, 2%% misch metal, ba ance magnesium. As cast; 6. 0 11'. 5 5. 0 0.7% Zr, 2 4% Zn, 2%% dldymium, balance magnesium. As cast 6.3 12.0 9.0 0.7% Zr, 4%% Zn, 2% Iqlsch' metal JaIEHCG IIIBQDGSIUJIII.

Heat treated-24 hrs. at 330? O. 8. 2 12. 4 3. 5 O.-7%"Zr; 4%% Zn, 2% didym= ium, balance magnesium. Heattreated 24 hrs..at.330 C. 8.4 14.0 5.0

CreepResistance Alloy Creep Rate per hour at 200 C.

ments of the yttrium sub-group of rare earth metals.

2. A magnesium base alloy, consisting essentially of at least 85% magnesium and at least 0.4% zirconium and from 0.5150 eper cent of rare earth metals of which neodymium constitutes at least and in which lanthanum and cerium do not exceed 25% together; the balance of. the rare earth metals being praseodymium and small quantities of samarium and traces of elements 01fv theyt-trium sub-group of rare earth metals, betWeen OA and 0.9% zirconium in a condition soluble in hydrochloric acid consisting of'30; cc; of H61 of specific gravity 1.16 to .85 cc. ofwa'ter'; sufficient acid being added during dissolution to maintain the initial concentration.

' AL'ERED'CLAUDE JESSUP.

EDWARD FREDERICK E'MLEY. PHILIP ANDREW FISHER.

REFERENCES CITED 'The following references are of recordlin the file" of this patent:

UNITED STATES PATENTS Number Name Date 25.4203293 Becket al. May 13, 1947 1461,229 Murphy et al Feb. 8, 1 949 2,4645918' Ball et'al Mar. 22, 1949 FOREIGN PATENTS Number Country" Date.

- 511,137 Great. Britain Nov. 8,. 1938 113,802 Australia Sept-4, 1941 OTHER REFERENCES Ser. No. 369,749, Sauerwald A; PFC.) published June 15,1943, abandoned.

-'I romble-et a1.: treatise inComptesRendus, 1943,. pages 603-605, inclusive (page 605' relied upon). 

1. A MAGNESIUM BASE ALLOY, CONSISTING ESSENTIALLY OF AT LEAST 85% MAGNESIUM AND AT LEAST 0.4% OF ZIRCONIUM AND FROM 0.5% TO 4% OF RARE EARTH METALS OF WHICH NEODYMIUM CONSTITUTES AT LEAST 50%, AND IN WHICH LANTHANUM AND CERIUM DO NOT EXCEED 25% TOGETHER, THE BALANCE OF THE RARE EARTH METALS BEING PRASEODYMIUM AND SMALL QUANTITIES OF SAMARIUM AND TRACES OF ELEMENTS OF THE YTTRIUM SUB-GROUP OF RARE EARTH METALS. 